This invention relates to antistatic resin composition with transparency comprising polycarbonate or polymethyl methacrylate and a heat resistant antistat.
Synthetic macromolecular materials are generally hydrophobic. As a result, they tend to become electrostatically charged and this property is a serious obstacle not only in the production processes of such materials but also in using products made therefrom. In the past, electrically conductive agents such as carbon and metallic particles or surfactants were used in various attempts to reduce electrostatic charges of synthetic macromolecular materials by mixing them internally together or by coating the material with an agent. These methods by electrically conductive agents are not generally feasible for many reasons such as the large amount of agents which must usually be used, the difficulty in adding them to a material, the difficulty in obtaining a transparent product and the high cost of such conductive agents. Thus, these agents can be used only in limited situations.
By contrast, since there are many antistates having surfactants as their main constituent, appropriate ones may be selected therefrom according to the situation. In fact, many of the type to be internally added have been considered and tried. When used as an internally applied antistat, however, anionic surfactants are difficult to handle because they are inferior in compatibility and uniform dispersibility or tend to decompose or deteriorate when heated. Cationic surfactants containing quaternary nitrogen in their molecules and amphoteric surfactants, on the other hand, can be used only in limited situations because they are extremely poor in heat resistance although their antistatic characteristics are good. As for non-ionic surfactants, they are relatively superior to the aforementioned ionic surfactants regarding compatibility with synthetic macromolecular materials but tend to be weak in antistatic characteristics and their effects disappear with time at normal or high temperatures. Although metal salts of organic sulfonic acids have been reported especially as internally applied antistats for polycarbonate and polyester resins which are molded at high temperatures (West German Patent 3,004,017), they are not sufficient in compatibility with resins or heat resistance. One adverse consequence of insufficient compatibility is that transparency characteristics of certain macromolecular materials such as polycarbonate are lost with such antistats. There has also been a report on using phosphonium salts or organic sulfonic acids having halogen substituent as a flame retardant (U.S. Pat. No. 4,093,589) but they are not to be expected to serve as antistats at all.